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用Java实现串口通信(windows系统下),需要用到sun提供的串口包 javacomm20-win32.zip。其中要用到三个文件,配置如下:
1.comm.jar放置到 JAVA_HOME/jre/lib/ext;
2.win32com.dll放置到 JAVA_HOME/bin;
3.javax.comm.properties 两个地方都要放
jre/lib(也就是在JAVA文件夹下的jre)
JAVA_HOME/jre/lib
说一下我应用的环境。电子秤称重时,计算机通过串口给称重控制显示器发送一次命令“R”,控制显示器则发送一次重量数据给串口,计算机再读取将数据显示在网页上。这样就构成了一个实时称重系统。
读写串口的代码如下:
- package com.chengzhong.tools;
- import java.io.*;
-
- import javax.comm.CommPortIdentifier;
- import javax.comm.*;
-
- /**
- *
- * This bean provides some basic functions to implement full duplex
- * information exchange through the serial port.
- *
- */
-
- public class SerialBean
- {
-
- public static String PortName;
- public static CommPortIdentifier portId;
- public static SerialPort serialPort;
- public static OutputStream out;
- public static InputStream in;
-
- //保存读数结果
- public static String result="";
- public static int openSignal=1;
-
- /**
- *
- * Constructor
- *
- * @param PortID the ID of the serial to be used. 1 for COM1,
- * 2 for COM2, etc.
- *
- */
-
- public SerialBean(int PortID)
- {
- PortName = "COM" +PortID;
-
- }
-
- /**
- *
- * This function initialize the serial port for communication. It starts a
- * thread which consistently monitors the serial port. Any signal captured
- * from the serial port is stored into a buffer area.
- *
- */
-
- public int Initialize()
- {
-
- openSignal=1;
-
- try
- {
-
- portId = CommPortIdentifier.getPortIdentifier(PortName);
-
-
- try
- {
- serialPort = (SerialPort)
- portId.open("Serial_Communication", 2000);
-
- } catch (PortInUseException e)
- {
-
- if(!SerialBean.portId.getCurrentOwner().equals("Serial_Communication"))
- {
-
- openSignal=2; //该串口被其它程序占用
- }else if(SerialBean.portId.getCurrentOwner().equals("Serial_Communication")){
-
- openSignal=1;
- return openSignal;
- }
-
- return openSignal;
- }
-
- //Use InputStream in to read from the serial port, and OutputStream
- //out to write to the serial port.
-
- try
- {
- in = serialPort.getInputStream();
- out = serialPort.getOutputStream();
-
- } catch (IOException e)
- {
-
- openSignal=3; //输入输出流错误
- return openSignal;
-
- }
-
- //Initialize the communication parameters to 9600, 8, 1, none.
-
- try
- {
- serialPort.setSerialPortParams(9600,
- SerialPort.DATABITS_8,
- SerialPort.STOPBITS_1,
- SerialPort.PARITY_NONE);
- } catch (UnsupportedCommOperationException e)
- {
-
- openSignal=4; //参数不正确
- return openSignal;
- }
- } catch (NoSuchPortException e)
- {
-
- portId=null;
- openSignal=5; //没有该串口
-
- return openSignal;
- }
-
- // when successfully open the serial port, create a new serial buffer,
- // then create a thread that consistently accepts incoming signals from
- // the serial port. Incoming signals are stored in the serial buffer.
-
-
- // return success information
-
- return openSignal;
- }
-
-
-
- /**
- *
- * This function returns a string with a certain length from the incoming
- * messages.
- *
- * @param Length The length of the string to be returned.
- *
- */
-
- public static void ReadPort()
- {
- SerialBean.result="";
- int c;
- try {
- if(in!=null){
- while(in.available()>0)
- {
- c = in.read();
- Character d = new Character((char) c);
- SerialBean.result=SerialBean.result.concat(d.toString());
- }
- }
-
- } catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
-
- }
-
- /**
- *
- * This function sends a message through the serial port.
- *
- * @param Msg The string to be sent.
- *
- */
-
- public static void WritePort(String Msg)
- {
-
- try
- {
- if(out!=null){
- for (int i = 0; i < Msg.length(); i++)
- out.write(Msg.charAt(i));
- }
-
- } catch (IOException e) {
-
- return;
-
- }
- }
-
- /**
- *
- * This function closes the serial port in use.
- *
- */
-
-
- public void ClosePort()
- {
-
- serialPort.close();
- }
- }
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这样通过 SerialBean.result 就可得到读数结果。
至于把数据放到网页上,就要用到Ajax了,这里用到了一个Ajax框架dwr, dwr类Put.java 如下:
- package com.chengzhong.dwr;
-
- import java.io.IOException;
-
- import com.chengzhong.tools.Arith;
- import com.chengzhong.tools.SerialBean;
-
- public class Put {
-
- //2011.9.17
- public String write(){
-
-
- //发送指令R,仪器发送一次净重数据
- SerialBean.WritePort("R");
- //读取数据
- SerialBean.ReadPort();
- String temp=SerialBean.result.trim(); //我这里temp是形如 wn125.000kg 的数据
- if(!temp.equals("") && temp.length()==11)
- {
- return (change(temp)).toString();
-
- }else{
- return "";
- }
-
-
- }
-
- //响应开始称重
- public String startWeight(String num){
-
- int n=Integer.parseInt(num.trim());
- SerialBean SB = new SerialBean(n);
- SB.Initialize();
- return SerialBean.openSignal+""; //返回初始化信息
-
- }
-
- //响应停止称重
-
- public void endWeight(){
-
-
-
- try {
- //关闭输入、输出流
- SerialBean.in.close();
- SerialBean.out.close();
- } catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
-
- if(SerialBean.serialPort!=null){
- SerialBean.serialPort.close(); //关闭串口
- }
-
- SerialBean.serialPort=null;
- SerialBean.portId=null;
-
- SerialBean.result="";
-
- }
- /**
- * 将形如 wn125.000kg 格式的重量转换为 125.000 (kg)(四舍五入,小数点后保留两位)
- */
- public String change(String source){
- Double result=0.0;
- String s1=source.substring(2,9);
- try{
- result=Double.parseDouble(s1);
- result=Arith.round(result,2);
- }catch(Exception e){
- e.printStackTrace();
- return "";
- }
-
- return result.toString();
- }
-
-
-
- }
-
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注:Arith.java是一个java 的高精度计算文件。
- package com.chengzhong.tools;
- import java.math.BigDecimal;
-
- /**
- * 由于Java的简单类型不能够精确的对浮点数进行运算,这个工具类提供精
- * 确的浮点数运算,包括加减乘除和四舍五入。
- */
-
- public class Arith{
- //默认除法运算精度
- private static final int DEF_DIV_SCALE = 10;
- //这个类不能实例化
- private Arith(){
- }
-
- /**
- * 提供精确的加法运算。
- * @param v1 被加数
- * @param v2 加数
- * @return 两个参数的和
- */
- public static double add(double v1,double v2){
- BigDecimal b1 = new BigDecimal(Double.toString(v1));
- BigDecimal b2 = new BigDecimal(Double.toString(v2));
- return b1.add(b2).doubleValue();
- }
- /**
- * 提供精确的减法运算。
- * @param v1 被减数
- * @param v2 减数
- * @return 两个参数的差
- */
- public static double sub(double v1,double v2){
- BigDecimal b1 = new BigDecimal(Double.toString(v1));
- BigDecimal b2 = new BigDecimal(Double.toString(v2));
- return b1.subtract(b2).doubleValue();
- }
- /**
- * 提供精确的乘法运算。
- * @param v1 被乘数
- * @param v2 乘数
- * @return 两个参数的积
- */
- public static double mul(double v1,double v2){
- BigDecimal b1 = new BigDecimal(Double.toString(v1));
- BigDecimal b2 = new BigDecimal(Double.toString(v2));
- return b1.multiply(b2).doubleValue();
- }
-
- /**
- * 提供(相对)精确的除法运算,当发生除不尽的情况时,精确到
- * 小数点以后10位,以后的数字四舍五入。
- * @param v1 被除数
- * @param v2 除数
- * @return 两个参数的商
- */
- public static double div(double v1,double v2){
- return div(v1,v2,DEF_DIV_SCALE);
- }
-
- /**
- * 提供(相对)精确的除法运算。当发生除不尽的情况时,由scale参数指
- * 定精度,以后的数字四舍五入。
- * @param v1 被除数
- * @param v2 除数
- * @param scale 表示表示需要精确到小数点以后几位。
- * @return 两个参数的商
- */
- public static double div(double v1,double v2,int scale){
- if(scale<0){
- throw new IllegalArgumentException(
- "The scale must be a positive integer or zero");
- }
- BigDecimal b1 = new BigDecimal(Double.toString(v1));
- BigDecimal b2 = new BigDecimal(Double.toString(v2));
- return b1.divide(b2,scale,BigDecimal.ROUND_HALF_UP).doubleValue();
- }
-
- /**
- * 提供精确的小数位四舍五入处理。
- * @param v 需要四舍五入的数字
- * @param scale 小数点后保留几位
- * @return 四舍五入后的结果
- */
- public static double round(double v,int scale){
-
- if(scale<0){
- throw new IllegalArgumentException(
- "The scale must be a positive integer or zero");
- }
- BigDecimal b = new BigDecimal(Double.toString(v));
- BigDecimal one = new BigDecimal("1");
- return b.divide(one,scale,BigDecimal.ROUND_HALF_UP).doubleValue();
- }
- }
-
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网页页面上:
- <script type="text/javascript" src="/ChengZhong/dwr/engine.js"></script>
- <script type="text/javascript" src="/ChengZhong/dwr/util.js"></script>
- <script type='text/javascript' src='/ChengZhong/dwr/interface/ss.js' ></script>
- <script type='text/javascript' >
- var ID;
- function begin(){
- ID=window.setInterval('get()',500); //每隔半秒自动调用 get(),取得毛重数据填入文本框中
- }
- function get()
- {
- ss.write(readIt); //调用dwr类 Put.java 中的write方法
- }
- function readIt(Data){
-
- if(Data!=null && Data!="")
- {
- document.getElementById("mzBF").value=Data;
- }
-
- }
- </script>
-
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dwr的使用就不说了
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